Ontario Provincial Police are warning motorists to stay off the roads unless absolutely necessary due to a savage ice storm that slammed southern Ontario with ice pellets and freezing rain on Sunday, knocking off power to over 40,000 people.

Provincial police said there were roughly 750 crashes on highways surrounding Toronto on Saturday, and there had been nearly 700 more by early Sunday afternoon.

“We would prefer the highways to be empty and are encouraging all non-essential travel to be postponed,” said Ontario Provincial Police (OPP) Sgt. Kerry Schmidt in an update Sunday morning.

Schmidt said OPP have responded to well over 1200 overall collisions since the storm began on Saturday. The QEW westbound was closed at Ford Drive due to a jackknifed tractor trailer earlier in the day Sunday. There was also a report of another jackknifed tractor trailer in the London area around the same time. Fortunately, no crashes have resulted in any major injuries.

Rain, freezing rain and ice pellets continued to fall overnight and into Sunday across southern and central Ontario as a massive, slow-moving storm system moves across the region.

WATCH: Mike Arsenault is tracking a major ice storm that has ravaged southern Ontario throughout the weekend, saying that some southern parts are transitioning from freezing rain to rain over night.

The system is affecting an area from Windsor, Ont. to Quebec, and from North Bay, Ont. to Lake Ontario.

Environment Canada has issued rain and freezing rain warnings across the GTA.

Hydro One said that more than 42,000 customers were without power as of early Sunday evening, mainly in southwestern Ontario. They said extra crews were working to address the outages, saying that fallen trees and broken poles were causing most of the issues.

Crews face hazardous conditions and significant damage such as broken poles, downed lines & trees as they work to restore power to over 42,000 customers. Teams from our contact centre to lines, forestry and damage assessors are coming together to help with relief efforts #ONstormpic.twitter.com/mZiBWTqzVr

Toronto Hydro spokesperson Tori Gass told Global News that they have not received any weather related outages in the city as of yet. Gass said that almost three times the amount of crews are out compared to a normal weekend. They have also staffed additional people in the control and call centre as well.

WATCH: A camera caught a dog sprinting out of the way as a large branch broke off a tree, narrowly missing the dog as an ice storm punished southern Ontario.

Toronto’s downtown Billy Bishop airport cancelled all departing flights and received only one arrival all day on Sunday, while more than 600 flights were cancelled at the larger Pearson International Airport. Dozens of flights were also cancelled or delayed at Ottawa International Airport.

Freezing rain continues to affect the region. Airport operations will be very slow due to weather. Please be prepared for possible cancellations/delays. We’re working w. your carriers to keep operations moving safely. Check flight status w. airline or at https://t.co/3zG1zUKFDn.

Toronto Transit Commission (TTC) spokesperson Hayley Waldman told 640 Toronto that subway service, streetcars and buses are moving the “best they can due to the inclement weather.” She said additional streetcars have been added to routes along the downtown core to “avoid any icy buildup on the overheads.”

Waldman said that all streetcars on route 512 on St. Clair have been replaced by buses. Those streetcars are being used as additional cars on other routes.

“We actually transitioned not specifically because it was especially treacherous, but just because it is a route that’s easy for crews to get to in the event of an issue,” she said. “We use those additional streetcars from that route on some of our more south routes because the additional volume of streetcars helps us prevent ice buildup on the overhead streetcar wires.

WATCH: An unseasonal ice storm has caused unsafe road conditions in the GTA. As Erica Vella reports, Toronto Mayor John Tory is asking people to stay home, unless they absolutely have to.

Additionally, sliders have been added to “roughly” every fifth car, Waldman said, which help with the buildup of ice as well. The TTC also has extra crews out on the roads and extra customer service representatives at the “more popular hubs” around the city.

“Any problems that arise, we are ready to tackle them. Safety is our number one priority, we’re just going to keep moving the best we can and make sure we get all of our customers to their final destinations,” she said.

Driving along York Mills — roads are messy. Lots of slush and snow. The city says approx. 80 salter trucks are out (30 of which are plow-enabled) but very slippery conditions. Stay home if you can. #onstormpic.twitter.com/tgeGesRxnv

Global News meteorologist Anthony Farnell said the storm will continue on throughout the day, with the ice pellets changing back to freezing rain by late morning or early afternoon.

“Ice buildup on trees and power lines will be most significant cross the Niagara Escarpment region and through the west of the GTA.”

WATCH: Fire fighters worked to free a tractor trailer truck that went off the road on Highway 6 in Hamilton on Sunday.

Environment Canada issued a wind warning for the city of Toronto late Sunday afternoon, saying wind gusts up to 100 kilometres an hour could occur along the Lakeshore.

High winds could “cause damage to buildings, such as to roof shingles and windows. High winds may toss loose objects or cause tree branches to break,” the statement read.

Farnell said thunderstorms are also likely in the forecast later Sunday night once the ice pellets and freezing rain turn into “heavy rain.”

WATCH: Toronto Mayor John Tory tells residents to stay home and if they have to go out to use public transit.

Global News meteorologist Ross Hull said Environment Canada has issued rainfall warnings for “the GTA stretching east and toward the southwest that call for 25-plus millimetres of rain,” but for those areas that see thunderstorms, they could possibly see 45 to 50 millimetres.

Transportation Services General Manager Barbara Gray told reporters on Sunday that the city has deployed 80 salters onto its streets, 30 of which are plow-enabled.

“We’ve just got done plowing the DVP, making sure the catch basins stay clear so that when we have flooding and additional rain that happens tonight and into tomorrow, that those catch basins do their job,” Gray said, adding the city has both contracted and in-house staff working on a rotation on a 24-hour basis.

“If you plow all that slush and ice pellets onto the side of the road, it dramatically increases the chances we would have a real flooding problem if we have heavy rains later on,” Mayor John Tory said at the news conference.

“No one would thank us if we plowed every millimetre of snow off the streets and ended up causing a catastrophic flooding problem tomorrow morning,” he said.

On top of expressways and roadways, Gray said plows, salters and sidewalk crews are working on clearing bus stops, as well as high-pedestrian traffic areas and bikes lanes.

Tory also echoed Schmidt’s earlier words and encouraged residents to stay home and off the roads.

“If people could stay off the roads today, that would be best,” he said. “It would just be helpful if people wouldn’t be on the roads today.”

Meanwhile, a main concern is Monday when “the big melt” will be underway, Farnell said. With temperatures getting warmer, the meteorologist said he is concerned about river flooding, as well as street flooding with sewers and drains clogged with ice and snow.

The Toronto and Regional Conservation Authority is also warning that some creeks and rivers could flood by late Sunday due to the heavy rain.

Farnell warns motorist to give themselves plenty of time to get to work Monday morning.

Due to the special weather alert issued by Environment Canada and out of concern for the safety of all involved, all Humber College campuses and the University of Guelph-Humber will be closed on Saturday, April 14 and Sunday, April 15, 2018. More info: https://t.co/kkWkN6SFkm

McMaster remains closed due to inclement weather. The University hopes to reopen Sun. April 15 at 1:00 pm. A final decision will be made Sun. morning around 10:00 am and will be shared via social media & Daily News. Commons and Mary Keyes food service will open at 10:00 am Sunday